EP0092569B1 - A fir-type balance filter incorporated in the transmitter-receiver unit in a telecommunication system - Google Patents

A fir-type balance filter incorporated in the transmitter-receiver unit in a telecommunication system Download PDF

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Publication number
EP0092569B1
EP0092569B1 EP82903351A EP82903351A EP0092569B1 EP 0092569 B1 EP0092569 B1 EP 0092569B1 EP 82903351 A EP82903351 A EP 82903351A EP 82903351 A EP82903351 A EP 82903351A EP 0092569 B1 EP0092569 B1 EP 0092569B1
Authority
EP
European Patent Office
Prior art keywords
filter
group
memory
signal
unit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82903351A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0092569A1 (en
Inventor
Bengt Roland Carlqvist
Lars Tommy Edvard Svensson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of EP0092569A1 publication Critical patent/EP0092569A1/en
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Publication of EP0092569B1 publication Critical patent/EP0092569B1/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
    • H04B3/23—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
    • H04B3/23—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers
    • H04B3/231—Echo cancellers using readout of a memory to provide the echo replica
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H17/00—Networks using digital techniques
    • H03H17/02—Frequency selective networks
    • H03H17/06—Non-recursive filters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
    • H04B3/23—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers
    • H04B3/238—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers using initial training sequence

Definitions

  • the present invention relates to a balance filter included in a telecommunication system for duplex data transmission. More precisely, there is intended a filter which is incorporated in an echo canceller for inhibiting the effect of an echo signal from the transmit side via the hybrid coupler to the receive side.
  • a method and apparatus are described in the Swedish Patent Application No 8106444-6 for achieving adaptive echo cancellation.
  • the principle of the apparatus will be apparent from the appended Figure 1.
  • the data sequences b n and an are transmited on the conductor pair to and from the remote end, respectively. There arrive at the local end receive units not only the signal w(t) from the remote end but also a signal h(t) coming from the local transmitter S. In practical cases, the amplitude of the h(t) signal may be very much greater than that of the w(t) signal.
  • a signal y(t) is subtracted from the received signal.
  • the former is the output signal from the balance filter B, the input signal of which comes from the data sequence b n .
  • the balance filter is adjusted adaptively with the aid of the correction unit KB so that y(t) and h(t) become equal in the sampling instants kT. After subtraction there only remains the w(t) signal from which data from the remote end can be extracted.
  • the balance filter should be of the FIR type (Finite Impulse Response).
  • FIR Finite Impulse Response
  • the output signal of such a filter is defined thus: where the parameters of the filter are represented by the vector and the input signal is written in vector form:
  • the correction unit KB calculates a correction of the filter narameters: where c(k) is the filter parameter vector at the time kT and Ac(k) is a correction vector.
  • the correction vector will be: i.e. only one of the parameters is updated at each correction occasion.
  • the transmitter unit S, coupler G and lowpass filter LP as well as other units not shown in Figure 1 in the transmitter-receiver unit give rise to non-linearities.
  • the signal w(t) coming to the hybrid coupler G from the remote end is comparatively weak.
  • the signal h(t) from the transmitter unit S through the coupler G (the leak signal) is, on the other hand, at least at the beginning of transmit-receive, relatively strong before echo cancellation has managed to come into action. In practical cases, the signal h(t) may be much greater than w(t), e.g. a hundred times as great.
  • Remaining parts N2 may utilize table look-up or vector multiplication. Since the value N1 can be comparatively small, the total filter requires considerably less memory space, simultaneously as convergence will be quicker than if a conventional table look-up technique were utilized for the whole filter.
  • the object of the present invention is to provide a balance filter included in a transmitter-receiver unit with adaptive echo cancellation, which has a filter structure such that non- linearities in the transmitter-receiver path present in practical cases may be compensated.
  • the balance filter is thereby characterized as will be apparent from the characterizing features in claim 1.
  • the advantage of the filter in accordance with the invention is, apart from compensating nonlinearities in the leak signal, that little memory space is required and a shortened convergence time in the filter is obtained.
  • the block diagram of Figure 1 has been previously described under the title "Background art".
  • the new implementation of the balance filter B in Figure 1 will be seen from the block diagram of Figure 2.
  • the input to the transmitter unit S on which the data symbols b k occur is connected to a first delay circuit T1 included in the balance filter B.
  • the balance filter contains two groups I and II of delay circuits.
  • the first group I includes the two delay circuits T1 and T2 and the other group II the circuits T3, T4 and T5. It is naturally possible to extend the number of delay circuits as well as the number of groups.
  • Each circuit T1­T5 delays the incoming value b k , b k-1 , ... a time T corresponding to the transmitted data speed.
  • group I there is also included an addressing unit AE1, the inputs (in this case 3) being connected to the inputs of the delay circuits T1 T3.
  • the unit AE1 is connected by its output to the input of a memory unit M1 storing the coefficients, c j in table form, said coefficients constituting the filter parameters.
  • the values b k , b k-1 , b k-2 are applied to the addressing unit AE1, where a given address is formed in response to the value of the symbols b k , b k-1 , b k-2 .
  • the address thus formed points out in the memory unit M 1 a given coefficient c k which occurs on the output of the unit M1.
  • group II in the balance filter B also utilizes table look-up as does group I.
  • group I a given coefficient Cj is pointed out in the memory unit M2 from the addressing unit AE2 in response to values of the symbols b k-3 , b k-4 , b k-5 .
  • the coefficients c k from group I and c j from group II are applied to both inputs of a summing circuit A2.
  • the output of this circuit is connected to a digital-to-analogue converter DA for converting the digital sum c k +C j to the analogue signal y(t).
  • This signal is the correction signal for the analogue signal h(t)+w(t) coming from the coupler G to the receive side and, as above, h(t) is the leak signal and w(t) the remote signal.
  • the signal r k is applied to the detector D on the receive side to form an estimation of the transmitted data flow an from the remote end. Both flows r k and b k have to be uncorrelated for correct balancing to be performed by the balance filter.
  • Two correction units KB1 and KB2 operating in parallel are therefore connected between the detector D and sampling unit SH.
  • Both units KB1 and KB2 have an input connected to the input of the transmitter unit S and thus receive the data flow b k .
  • the output of KB1 is connected to the memory unit M1 and the output of KB2 is connected to the unit M2, to send correction signals to these units.
  • an output of each of the memory units M1, M2 is connected to an input on the correction units KB1, KB2, for supplying the coefficient c j , c k which is to be corrected.
  • a correlation is made of the values r k from the sampling unit SH.
  • the correlation is performed in the units KB1, KB2 by the coefficient c j , c k (which is to be corrected) being pointed out by the data values b k , b k-1' b k-2 (for KB1) and b k-3 , b k-4 , b k-5 (for KB2, correction of the pointed-out coefficient taking place in. response to the value of r k , as described in the above-mentioned patent application.
  • Group II according to Figure 2 which carries out table look-up, can be replaced by a digital filter according to Figure 3, for carrying out vector multiplication.
  • the filter of Figure 3 conventionally comprises delay circuits T3, T4, T5, the inputs of which, together with the output of T5, are connected to a summing circuit A3 via the controllable and multipliers MP1 ⁇ MP4.
  • the output of the summing circuit A3 is connected to the summing circuit A2 in Figure 2.
  • the multipliers MP1-MP3 multiply the delayed values: by the coefficients c 1 , c 2 , c 3 the expression being formed after addition, this forming the output signal from the digital filter and corresponding to the output signal from the memory unit M2 in Figure 2.
  • the coefficients are supplied to the multipliers MP1-MP4 from a memory unit M3 connected to the correction unit KB2 for updating, similar with updating of the coefficients in the memory unit M2 according to Figure 2.
  • the correlation is carried out in the units KB1, KB2 by summing the products of the values b k and r k over a given number of sampling intervals, i.e.
  • a diagram is shown in Figure 4 for more closely illustrating the problem with non-linearity in the transmitter-receiver part.
  • the diagram shows the impulse response g(t) of the impulse occurring on the transmit side and from the transmit side to receive side via the units S, G, LP.
  • the leak signal h(t) can then be denoted: and if N data symbols are considered and if the signal paths S, G, LP is linear.
  • a data symbol thus gives rise to the components b k-1 . g 2 , b k-2 ' g 2 etcetera.
  • h(k) may be denoted
  • the denotation of the h(k) can be approximately a nonlinear portion and a linear portion according to:
  • the balance filter is divided up according to the above in a first group I, utilizing table look-up and a second group II utilizing table look-up or vector multiplication.
  • Group I contains a filter part which by means of table look-up imitates the nonlinear function f 1 (b k , b k-1 , b k-2 , g 1 g 2 g 3 )
  • group II contains an FIR-type transversal filter which imitates the linear function b k-3 ⁇ g 4 +b k-4 ⁇ g 5 +].
  • group II also comprises a filter utilizing table look-up. Since in table look-up the output signal of the filter group I (or II) does not need to be linearly related, the nonlinear Dart of h(t) can be imitated by the .
  • the advantage of dividing up the balance filter in two (or more) parts is that quicker updating of the filter coefficients c k , c. in the memory units M1, M2 can be obtained.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Mathematical Physics (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Filters That Use Time-Delay Elements (AREA)
  • Circuits Of Receivers In General (AREA)
  • Selective Calling Equipment (AREA)
EP82903351A 1981-11-02 1982-11-02 A fir-type balance filter incorporated in the transmitter-receiver unit in a telecommunication system Expired EP0092569B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8106445A SE426765B (sv) 1981-11-02 1981-11-02 Balansfilter av fir-typ ingaende i sendar-mottagarenheten i ett telekommunikationssystem
SE8106445 1981-11-02

Publications (2)

Publication Number Publication Date
EP0092569A1 EP0092569A1 (en) 1983-11-02
EP0092569B1 true EP0092569B1 (en) 1984-10-24

Family

ID=20344931

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82903351A Expired EP0092569B1 (en) 1981-11-02 1982-11-02 A fir-type balance filter incorporated in the transmitter-receiver unit in a telecommunication system

Country Status (18)

Country Link
US (1) US4571719A (es)
EP (1) EP0092569B1 (es)
JP (1) JPS58501849A (es)
KR (1) KR870000629B1 (es)
AU (1) AU553371B2 (es)
BR (1) BR8207952A (es)
DE (1) DE3261072D1 (es)
DK (1) DK301783D0 (es)
ES (1) ES516966A0 (es)
FI (1) FI73104C (es)
IE (1) IE53760B1 (es)
IT (1) IT1153339B (es)
MX (1) MX152128A (es)
MY (1) MY100485A (es)
NO (1) NO157239C (es)
SE (1) SE426765B (es)
WO (1) WO1983001715A1 (es)
YU (1) YU244382A (es)

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1186764A (en) * 1982-06-23 1985-05-07 Akira Kanemasa Echo canceler
US4669116A (en) * 1982-12-09 1987-05-26 Regents Of The University Of California Non-linear echo cancellation of data signals
IT1208769B (it) * 1983-10-12 1989-07-10 Cselt Centro Studi Lab Telecom Teristiche varianti nel tempo procedimento e dispositivo per la cancellazione numerica dell eco generato in collegamenti con carat
NL8600817A (nl) * 1986-03-28 1987-10-16 At & T & Philips Telecomm Adaptief filter voor het vormen van een echokompensatiesignaal in een zend-ontvangstelsel voor het in duplexvorm bedrijven van digitale communicatie over een enkel geleiderpaar.
US4868874A (en) * 1986-04-18 1989-09-19 Hitachi, Ltd. Echo canceller
EP0255554B1 (de) * 1986-08-07 1991-05-08 Deutsche ITT Industries GmbH Nichtrekursives Digitalfilter
EP0280898A1 (de) * 1987-02-18 1988-09-07 Siemens Aktiengesellschaft Schaltungsanordnung zum Unterdrücken von Echosignalen
JP2581763B2 (ja) * 1988-06-15 1997-02-12 株式会社日立製作所 エコーキャンセラ
CA1315356C (en) * 1988-07-20 1993-03-30 Seiji Miyoshi Digital adaptive filter and method of convergence therein
AU614447B2 (en) * 1988-12-01 1991-08-29 Nec Corporation Echo canceller with means for determining filter coefficients from autocorrelation and cross-correlation coefficients
US4982428A (en) * 1988-12-29 1991-01-01 At&T Bell Laboratories Arrangement for canceling interference in transmission systems
DE19645054C2 (de) * 1996-10-31 1999-11-25 Sgs Thomson Microelectronics Vorrichtung und Verfahren zur Selektion von Adressenwörtern
US8718474B2 (en) * 2011-05-27 2014-05-06 Nec Laboratories America, Inc. Chromatic dispersion compensation using sign operations and lookup tables

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2277470A1 (fr) * 1974-07-03 1976-01-30 Cit Alcatel Dispositif de centrage d'un filtre transversal d'un annuleur d'echo
NL170688C (nl) * 1976-06-28 1982-12-01 Philips Nv Inrichting voor simultane tweerichtingsdatatransmissie over tweedraadsverbindingen.
IT1091970B (it) * 1977-01-17 1985-07-06 Trt Telecom Radio Electr Dispositivo digitale per la cancellazione di echi,per un modulatore/demodulatore,per la trasmissione di dati mediante modulazione di una portante
DE2729109A1 (de) * 1977-06-28 1979-01-11 Siemens Ag Schaltungsanordnung zur kompensation von echos in nichtsynchronen traegerfrequenzsystemen
JPS54157407A (en) * 1978-06-02 1979-12-12 Hitachi Ltd Level control unit for time-division exchange
US4268727A (en) * 1979-03-14 1981-05-19 International Telephone And Telegraph Corporation Adaptive digital echo cancellation circuit
FR2479617A1 (fr) * 1980-03-26 1981-10-02 Trt Telecom Radio Electr Annuleur d'echo pour signal d'echo a phase variable
US4425483A (en) * 1981-10-13 1984-01-10 Northern Telecom Limited Echo cancellation using transversal filters

Also Published As

Publication number Publication date
NO157239B (no) 1987-11-02
WO1983001715A1 (en) 1983-05-11
EP0092569A1 (en) 1983-11-02
YU244382A (en) 1985-03-20
ES8308178A1 (es) 1983-08-01
FI73104B (fi) 1987-04-30
MY100485A (en) 1985-12-31
NO157239C (no) 1988-02-10
IT1153339B (it) 1987-01-14
KR840002599A (ko) 1984-07-02
AU553371B2 (en) 1986-07-10
IT8224026A0 (it) 1982-11-02
BR8207952A (pt) 1983-10-04
NO832421L (no) 1983-07-01
IE822606L (en) 1983-05-02
MX152128A (es) 1985-05-30
ES516966A0 (es) 1983-08-01
IE53760B1 (en) 1989-02-01
FI73104C (sv) 1987-08-10
KR870000629B1 (ko) 1987-03-26
FI832229A0 (fi) 1983-06-17
DK301783A (da) 1983-06-30
SE426765B (sv) 1983-02-07
FI832229L (fi) 1983-06-17
DE3261072D1 (en) 1984-11-29
US4571719A (en) 1986-02-18
DK301783D0 (da) 1983-06-30
AU9122182A (en) 1983-05-18
JPS58501849A (ja) 1983-10-27

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